The compounds prepared by the process of the present invention have been described in European application No. 187,376 as antibacterial agents.
British application No. 2,170,804 describes a process for producing 1-aryl-1,4-dihydro-4-oxo-1,8-naphthyridines and intermediates thereof as shown below. ##STR1## where R.sup.1 is hydrogen or carbonyl protecting group;
R.sup.2 is halogen or an organic group attached via an O or N atom; PA1 X is hydrogen or fluorine. PA1 R.sub.1 is a lower alkyl of from one to four carbon atoms, cycloalkyl of from three to six carbon atoms, or substituted cycloalkyl; and PA1 R.sub.2 is F, Cl, Br, or CF.sub.3 ; which comprises:
These are prepared from ##STR2## via an intermediate where COOR.sup.1 is replaced by CO--CH.sub.2 COOR.sup.1.
The compounds produced by the novel process of this invention are themselves intermediates for the known antibacterial agent enoxacin which is described in U.S. Pat. No. 4,359,578.
The chemical name of enoxacin is 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-c arboxylic acid.
The novel process of the present invention has the advantage of requiring fewer steps as it utilizes a more direct route than methods known in the art. Furthermore, the new process has industrial applications as it may be used to produce large quantities of the desired compounds. Certain of the intermediates of the present process are themselves novel compounds.